A 20-year-old woman is claiming in a lawsuit that the father of her 3-month-old son is Justin Bieber, who, she says, she had unprotected sex with backstage during one of his shows at the Staples Center in LA.

Well, s**t just got real...

Bieber's camp is, of course, denying the story fully. "While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory and demonstrably false claims," his publicist said in a statement. "We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations."

The woman, Mariah Yeater, says she had unprotected sex with Bieber when she was 19 after one of his shows. She's asking that the court order Bieber to undergo a paternity test to prove that he is the father, and then for him to provide "reasonable child support, effective immediately."

Just gotta point out: If her claims are true, that would make her 19 at the time of the tryst, and him 16. Under California law, he would be underage, and she's basically just opened herself up to statutory rape charges.